Avoiding Autonegotiation Mismatches; Gbic Security And Identification - Cisco Catalyst 2950 Software Configuration Manual

Avoiding Autonegotiation Mismatches

Table 26-1 Conflicting Features
Port Group
Port Group
–
Port Security
No
SPAN Source Port
Yes
SPAN Destination No
Port
Connect to Cluster Yes
Protected Port Yes
802.1X Port
No
1. Switch Port Analyzer (SPAN) can operate only if the monitor port or the port being monitored is not a protected port.
Avoiding Autonegotiation Mismatches
The IEEE 802.3U autonegotiation protocol manages the switch settings for speed (10, 100, or
1000 Mbps) and duplex (half or full). Sometimes this protocol can incorrectly align these settings,
reducing performance. A mismatch occurs under these circumstances:
•
•
To maximize switch performance and ensure a link, follow one of these guidelines when changing the
settings for duplex and speed:
•
•
Note If a remote Fast Ethernet device does not autonegotiate, configure the duplex settings on the two ports
to match. The speed parameter can adjust itself even if the connected port does not autonegotiate. To
connect to a remote Gigabit Ethernet device that does not autonegotiate, disable autonegotiation on the
local device, and set the duplex and flow control parameters to be compatible with the remote device.

GBIC Security and Identification

Cisco-approved GBIC modules have a serial EEPROM that contains the module serial number, the
vendor name and ID, a unique security code, and a cyclic redundancy check (CRC). When a GBIC
module is inserted in the switch, the switch software reads the EEPROM to check the serial number,
vendor name, and vendor ID, and recomputes the security code and CRC. If the serial number, the vendor
name or ID, the security code, or CRC is invalid, the switch places the interface in an error-disabled state.
Catalyst 2950 Desktop Switch Software Configuration Guide
26-2
SPAN
Port Security Source Port
No Yes
– Yes
Yes –
No No
Yes Yes
No Yes
No Yes
A manually set speed or duplex parameter is different from the manually set speed or duplex
parameter on the connected port.
A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.
Let both ports autonegotiate both speed and duplex.
Manually set the speed and duplex parameters for the ports on both ends of the connection.
SPAN
Destination Port
No
No
No
–
Yes
1 1
Yes
No
Chapter 26
Connect to Protected
Cluster? Port
Yes Yes
Yes No
1
Yes Yes
Yes Yes
– Yes
Yes –
– –
Troubleshooting
802.1X Port
No
No
Yes
No
–
–
–
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